CssStyleDeclaration performance work

tools/dom/scripts/css_code_generator.py

 #!/usr/bin/python
 #
 # Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 """Generates CSSStyleDeclaration template file from css property definitions
 defined in WebKit."""
 
 import tempfile, os
@@ skipping 99 matching lines @@
 $endif
   }
 $if DARTIUM
 
   bool _hasProperty(String propertyName) =>
       _blink.BlinkCSSStyleDeclaration.$__propertyQuery___Callback_1(this, propertyName);
 $endif
 
   @DomName('CSSStyleDeclaration.setProperty')
   void setProperty(String propertyName, String value, [String priority]) {
+    return _setPropertyHelper(_browserPropertyName(propertyName),
+      value, priority);
+  }
+
+  String _browserPropertyName(String propertyName) {
+    String name = _readCache(propertyName);
+    if (name is String) return name;
     if (_supportsProperty(_camelCase(propertyName))) {
-      return _setPropertyHelper(propertyName, value, priority);
+      name = propertyName;
     } else {
-      return _setPropertyHelper(Device.cssPrefix + propertyName, value,
-          priority);
+      name = Device.cssPrefix + propertyName;
     }
+    _writeCache(propertyName, name);
+    return name;
   }
 
+$if DART2JS
+  static final _propertyCache = JS('', '{}');
+  static String _readCache(String key) =>
+    JS('String|Null', '#[#]', _propertyCache, key);
+  static void _writeCache(String key, String value) {
+    JS('void', '#[#] = #', _propertyCache, key, value);
+  }
+$else
+  static String _readCache(String key) => null;
+  static void _writeCache(String key, value) {}
+$endif
+
   static String _camelCase(String hyphenated) {
 $if DART2JS
     var replacedMs = JS('String', r'#.replace(/^-ms-/, "ms-")', hyphenated);
 
     var fToUpper = const JS_CONST(
         r'function(_, letter) { return letter.toUpperCase(); }');
     return JS('String', r'#.replace(/-([\da-z])/ig, #)', replacedMs, fToUpper);
 $else
     // The "ms" prefix is always lowercased.
     return hyphenated.replaceFirst(new RegExp('^-ms-'), 'ms-').replaceAllMapped(
         new RegExp('-([a-z]+)', caseSensitive: false),
         (match) => match[0][1].toUpperCase() + match[0].substring(2));
 $endif
   }
 
 $if DART2JS
   void _setPropertyHelper(String propertyName, String value, [String priority]) {
-    // try/catch for IE9 which throws on unsupported values.
-    try {
-      if (value == null) value = '';
-      if (priority == null) {
-        priority = '';
-      }
-      JS('void', '#.setProperty(#, #, #)', this, propertyName, value, priority);
-      // Bug #2772, IE9 requires a poke to actually apply the value.
-      if (JS('bool', '!!#.setAttribute', this)) {
-        JS('void', '#.setAttribute(#, #)', this, propertyName, value);
-      }
-    } catch (e) {}
+    if (value == null) value = '';
+    if (priority == null) priority = '';
+    JS('void', '#.setProperty(#, #, #)', this, propertyName, value, priority);
   }
 
   /**
    * Checks to see if CSS Transitions are supported.
    */
   static bool get supportsTransitions {
     return document.body.style.supportsProperty('transition');
   }
 $else
   void _setPropertyHelper(String propertyName, String value, [String priority]) {
@@ skipping 69 matching lines @@
       class_lines.append(annotated[base_css_name])
     class_lines.append("""
   void set %s(String value) {
     setProperty('%s', value, '');
   }
 """ % (camel_case_name, css_name))
 
   class_file.write(''.join(class_lines));
   class_file.write('}\n')
   class_file.close()